If you're in CT, Fritz can most probably do it for way less..
If you know what you want to replace (like just the chain and tensioner with guides) that will be about 4k ex labour.
BMW can suck it, because they sell the whole oil pump, while Fritz can rebuild it (yes, you can buy build kits)
Then it's labour....
PM me if you have questions, I've had a engine rebuilding done, and my pump rebuilt and I've had no issues...